This invention relates to the on-site in situ production of stable peracetic acid for use as a biocidal control agent. Biocidal agents are used to limit or prevent biological fouling in liquid systems or on the surfaces of equipment that come in contact with the liquid systems. In the absence of such agent, biologically fouled liquid systems suffer with unwanted process interferences and inefficiencies. In addition biologically fouled liquid systems may lead to product contamination and various health hazards.
Fouling generally refers to the presence of unwanted organic or inorganic material in the suspended water phase (bulk water) or the accumulation of such unwanted material deposits on various surfaces that come in contact with the liquid system. Fouling can be mineral (such as particulate scale accumulation) and/or biological (microbial contamination) in nature. Fouling occurs by a variety of mechanisms including deposition of air-borne and water-borne and water-formed contaminants, water stagnation, process leaks, and other factors. In some cases mineral fouling can induce biological fouling and vice versa.
Some sources of microbial contamination in industrial liquid systems include, but are not limited to, air-borne contamination, water make-up, process leaks and improperly cleaned equipment. Under these conditions, microorganisms can rapidly establish microbial communities on any wetted or semi-wetted surface of the liquid system. Once these microbial populations are present in the bulk water more than 99% of the microbes present in the water will be present on the surface in the form of biofilms.
Exopolymeric substances secreted from the microorganisms aid in the formation of biofilms as the microbial communities develop on the surface. These biofilms are complex ecosystems that establish a means for concentrating nutrients and offer protection for growth. Biofilms can accelerate scale, corrosion, and other fouling processes. Not only do biofilms contribute to reduction of system efficiencies, but they also provide an excellent environment for microbial proliferation that can include pathogenic bacteria. It is therefore important that biofilms and other fouling processes be reduced to the greatest extent possible to maximize process efficiency and minimize the health-related risks from water-borne pathogens.
Several factors contribute to the problem of biological fouling and govern its extent. Water temperature, water pH, organic and inorganic nutrients, growth conditions such as aerobic or anaerobic conditions, and in some cases the presence or absence of sunlight, etc. can play an important role. These factors also help in deciding what types of microorganisms might be present in the water system.
A number of prior art attempts have been made to control biological fouling in industrial processes. The most commonly used method is the application of biocidal compounds to the process waters. Many of these prior art attempts make use of halogen based and in particular, chlorine-based compositions of matter. Some examples include U.S. Pat. Nos. 5,976,386 and 3,254,952 and US Published Patent Application 2009/0311164. However for various reasons it is desirable to avoid the use of halogens in biocidal agents. Halogens tend to conduct unwanted side reaction with other chemicals in the process waters thereby limiting the efficacy of the biocidal application and that of the applied chemical with which the halogen reacts. Also, halogen based biocides can form disinfection by-products such as AOX (adsorbable organic halide) and THMs (trihalomethanes) and in some cases cause health concerns. Finally, halogen based chemistries raise several environmental concerns due to their high reactivity and formation of disinfection by-products.
Thus there is a clear need and utility for an improved biocidal agent. The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.